The portion of the blast furnace below its widest cross-section is called

stack:The portion of the blast furnace above its widest cross-section is called stack.

Bosh:The portion of the blast furnace below its widest cross-section is called bosh.

Throat: The charge is fed into the blast furnace through the throat.

Hearth: The hearth is the lowest, but the most important part of the blast furnace.